!)]ll MONOGRAPHS OF NORTH AMERICAN RODBNTIA. 



Gi m RIC CHARS. — Skull with the dorsal outline nearly straight; frontal 

 region lint or depressed; postorbitals triangular at base, with a long, spread- 

 ing, decurved point ; zygomatic arches moderately expanded, not widening 

 and diverging posteriorly; grinding-teeth rather small, the transverse and 

 antero-posterior diameters about equal, and the molar series very nearly 

 parallel ; occipital and interparietal crests well developed (in old age) ; ante- 

 orbital foramina sulit riangular, widest below, but not thrown outward. Size 

 large; body thick-set, broad, depressed ; check-pouches small; tail rather 

 shmt, bushy, not flattened ; ears small; nail of pollex broad, flat, or wanting; 

 pelage with long coarse hairs and thick under fur. Coloration generally yel- 

 lowish-gray, without, either distinct spots or stripes. 



The genus Arctomys differs from Cynomys in many quite important 

 features. In Arctomys, the dorsal outline of the skull is straight, or nearby 

 so, instead of highly arched, as in Cynomys; the zygomatic arches are rela- 

 tively smaller, and reach their greatest expansion near the middle instead of 

 at their posterior border; the grinding-teeth are small, in nearly parallel series, 

 and differ widely from those of Cynomys in shape and in mode of insertion. 

 In Arctomys, the molars are inserted nearly vertically, as in the true Squirrels; 

 in Cynomys, their insertion is quite oblique. In Arctomys, the triturating 

 surface of the crowns is nearly square, but the inner border is somewhat 

 narrowed, so that the teeth of the same series touch each other by their 

 crown surfaces for only two-thirds of their transverse breadth; in Cynomys, 

 the transverse breadth of the crowns is twice that of the autero-posterior, 

 and internally the teeth are so much narrowed that they abet closely tor only 

 half their transverse breadth, leaving internally deep openings between the 

 teeth. In Arctomys, the palate is broad and scarcely narrower at the last 

 molar than anteriorly, while in Cynomys the palate is rapidly and greatly 

 narrowed posteriorly. Hence Arctomys differs very widely from Cynomys in 

 respect to the size, form, and position of the molar teeth and the form of the 

 bony palate. In all these points, Arctomys is more Sciurine than is even 



orclies, genres et especes qui sunt Homme's duns cet ouvrage [Dents des Maiumiferes], avec uue syno- 

 uymie latine", occurs the following: — 



"54. Marmottes, arctomys. Ginel. 



" Marmotte des Alpes, Arctomys alpinus. Linn. 

 "Marmotte dn Canada, Arctomys empetra. Pall." 

 Wlint In' me. ins bj " Arctomys empetra Pall." is certainly not. clear, s.nce no original description of 

 Pallas's empetra bad at tins date (18:25) appeared, except Pallas's original account of bis Mus empetra. 

 Sabine's Arctomys empetra (1822) i^ Araomys numax. If Cuvier bad specimens of the "Marmotte da 

 Canada ", Ins " Arctomys empetra Pall." is doubtless also referable t<> .1. mOnax, 



